Cabin thermal control system

ABSTRACT

The present finding relates to a system for controlling a cabin at least thermally. The system ( 10 ) with energy recovery includes a first air treatment unit ( 20 ) suitable to collect external air and supplying air at least thermally controlled (air treated) in the cabin ( 12 ), a second air treatment unit ( 30 ) suitable to collect exhausted air from the cabin ( 12 ) and heat exchange means ( 43 ) configured to exchange heat between exhausted air and external cabin air supply. The system also includes air humidification means ( 45 ) suitable to humidify the exhausted air, to reduce, using evaporation enthalpy, the preset temperature of the exhausted air, and to supply the exhausted humidified air to the heat exchange means in order to optimize the recovery of energy. The finding also relates to an exhausted air treatment unit and to a method to control a cabin at least thermally.

FIELD OF THE INVENTION

This invention relates broadly to a cabin thermal control system withenergy recovery.

More particularly, this invention relates to thermohygrometric cabincontrol systems for painting cabins, surface preparation cabins, cleanrooms, etc.

STATE OF THE ART

Energy recovery systems to thermally or hygrometrically control varioustypes of cabins, such as painting cabins are known. These systemsinclude, generally, a first air treatment unit (first ATU) to supplyexternal air to the cabin and a second air treatment unit (second ATU)to extract exhausted air from the cabin. For example it is known that inthermohygrometric cabin control systems, which here are taken asreference for ease of description, the first ATU includes:

-   -   an air ventilation section in the cabin to external air into the        cabin;    -   a heating section to heat air, if required;    -   a cooling section to cool air, this section may be used also to        obtain the condensation and collection of water and therefore to        dehumidify the air;    -   a humidification section, to humidify the air and at a        predefined humidity level;    -   a post-heating section to cooperate with the humidification        section to allow the inlet of        air with a predefined temperature and humidity level into the        cabin; and that the second ATU includes, for example:    -   a cabin air extraction ventilation section to extract the        exhausted air from the cabin;    -   a cross-flow or rotating flow heat exchanger section to exchange        heat between the exhausted air and the external air to supply to        the cabin in order to obtain energy recovery from this exchange        of heat.

The Requester has observed that the recovery of energy for simplecross-flow of air into and out of the cabin is extremely low and that,therefore, cabin energy recovery systems should be improved in order toobtain a significantly better recovery.

In summary the Requester has observed that solving the technical problemof energy recovery optimization in cabin systems seems to be an urgentissue.

DESCRIPTION OF THE INVENTION

This invention aims at solving the above mentioned issue with cabinenergy recovery systems.

This technical problem is solved with the cabin thermal control systemas claimed.

This invention relates also to a method to recover energy in a cabinthermal control system.

The claims comprise an integral part of the technical knowledge suppliedhere about this invention.

According to a preferred form of execution, the system to control acabin at least thermally

includes upstream of a heat exchanger section that exchanges heatbetween exhausted air extracted from the cabin and external air tosupply to the cabin, an air humidification unit to lower the temperatureof the exhausted air and thus optimize the recovery of energy obtainablefrom the heat exchanger system.

According to a further characteristic of this invention, the method tocontrol a cabin at least thermally associates the phase of collectionfrom the cabin of exhausted air with a phase of humidification of theexhausted air in order to reduce, through evaporation enthalpy, thetemperature of the exhausted air and optimize the system's energyrecovery.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of this invention will become clear fromthe following description of a preferred production form, as anon-exhaustive example with the help of drawings, in which the elementsindicated with a same or similar numerical reference indicate componentswith the same or similar function and structure, and in which:

FIG. 1 Represents a block chart of the system according to theinvention.

DESCRIPTION OF A PREFERRED FORM OF EXECUTION

With reference to FIG. 1, a system 10 to control at least thermally acabin 12, according to this invention, includes, upstream of the cabin,a first air treatment unit (first ATU) 20 and downstream of the cabin asecond air treatment unit (second ATU) 30.

The first ATU 20, of known type, collects external air and lets air at acontrolled temperature and, according to this example, humidity (treatedair), into cabin 12 and includes, as an example, an air inletventilation section in cabin 20 a, a heating section 20 b, a coolingsection 20 c, a humidification section 20 d and a post-heating section20 e, all of known type and connected between them in a known manner.According to the preferred form of execution, the first ATU 20 has anair inlet conduit 21, connected to an air outlet of the second ATU 30and allows the collection of external air, and at least one air inletconduit 23 connected to cabin 12 to supply treated air to cabin 12.

The second ATU 30 extracts the air from cabin 12 and treats it in orderto recover, in an optimized way, energy useful to treat the air with thefirst ATU 20, as will be described below in detail.

It should be noted that in the description of system 10 according tothis invention, the configured sections are particularly taken intoaccount to obtain the cooling of the external air inlet into the cabin,as the invention has been developed to optimize the recovery of energyin said conditions, i.e., when the temperature of the air supplied fromthe outside is higher than the temperature of the air expected in thecabin and therefore the temperature of the air supplied to the cabinmust be reduced significantly to preset values.

The second ATU 30, according to the preferred form of execution,includes:

-   -   a section or extracted air treatment means 41, of known type, to        extract air from cabin 12 through an air extraction conduit 31        and filter it; this section may include on the outlet, an air        recirculation conduit 33, per se known, connected to conduit 21,        if air recirculation is present;    -   a heat exchanger section or heat exchange means 43, e.g.,        across-flow or rotating section, of known type, e.g., a        NOVAIR-CLINT model section RF14/3730/S/AL; the heat exchanger        section 43 is connected to the first ATU 20 through a conduit 21        and includes an external air inlet conduit 37 connected to an        external air intake 47 a, with interposed, preferably, a        filtering section 47, an outlet conduit 39 suitable to discharge        exhausted air outside with interposed, preferably, an emission        system or treatment section 49, of known type, suitable to        filter/eliminate polluting substances present in the exhausted        air;

Further, the second ATU 30, according to one of the characteristics ofthis invention, includes the following:

-   -   a section or humidification means 45, having an exhausted air        inlet conduit 34 connected to the section of extracted air        treatment 41 and a humidified exhausted air outlet conduit 35        connected to the heat exchanger section 43.

The humidification section 45, e.g., a NOVAIR-CLINT ADIABATIC SECTION200 mm model section is suited to humidify the exhausted air out of thecabin, thanks to simple water evaporation and using evaporationenthalpy, and is suited to noticeably lower, as will become clear later,

the temperature of the exhausted air extracted from cabin 12 beforebeing supplied to the second heat exchanger section 43.

It should be noted that in this description, as can be easily understoodby a technician of the field, the term conduit is used in a broad senseto indicate one or more conduits or tubes suited to transport fluids,e.g., air.

It should also be added that in this description two air treatment units(ATU) have been defined, for ease of description, but that, as can beeasily understood by a technician of the field, the sections describedmay be independent sections connected between them to execute the systemwithout requiring inclusion in corresponding air treatment units.

The system 10 described so far works as follows.

The air from the environment is pre-filtered into filter section 47 tothen go through heat exchanger section 43, crossing the exhausted airextracted from the cabin.

Once the air has passed through the heat exchanger section 43, it isextracted from the first ATU 20 in which its thermohygrometric controloccurs.

The air is supplied to cabin 12 to maintain preset thermohygrometricconditions in the cabin.

The extracted air treatment section 41 extracts “exhausted” air fromcabin 12 to supply to humidification section 45 and/or partiallyrecirculate it in the first ATU 20 through conduit 33.

The recirculation depends on possible air pollution occurred duringmanufacturing processes within cabin 12 and, according to executionvariations of this invention, may not be present.

The air not recirculated is treated by humidification section 45, cooledfurther and with a higher specific heat (SH), due to water evaporation,is sent to the heat exchanger section 43 to then be discharged into theenvironment or sent to an exhausted air treatment system 49 throughconduit 39.

The results of energy recovery are reported below following trial testsconducted with the system according to the invention, from which it canbe inferred that the presence of humidification section 45 enables thehighest energy recovery for system 10.

A cabin that operates for 16 hours daily with the following should betaken as reference:

-   -   85,000 m3/h air capacity (at 25° C. internal cabin conditions);    -   a cabin environment temperature of 25° C.;    -   a cabin environment relative humidity (RH) of 50+5% RH.

Summer conditions with a temperature of 35° C. and 50% RH should beassumed.

System without Humidification Section

The cross-flow heat exchanger section has:

-   -   cabin extraction airflow 77,872 Nm3/h corresponding to 85,000        m3/h at 25° C.    -   Temperature 25° C.;    -   Relative humidity 50±5%;    -   Cabin inlet airflow 77,872 Nm3/h, corresponding to 87,850 m3/h        at 35° C.;    -   Temperature 25° C.;    -   Relative humidity 50±5%;

Considering an average of 60% efficiency for the heat exchanger, energyrecovery is approximately 147,393 kCal/h, with a thermal differential ofapproximately 6° C. That is, the inlet air is cooled by 6° C., then aninlet air cooling is obtained from 35° C. to 29° C.

System with Humidification Section

If there is a humidification section, the exhausted extraction air ishumidified before going through the cross-flow exchanger.

In the assumed conditions, the humidification section may cool the airfrom 25° C. with RH=50%, to approximately 21° C. with RH=70%.

In this case, in the cross-flow exchanger, the following operatingconditions occur:

-   -   Cabin extraction airflow 77,872 Nm3/h corresponding to 85,000        m3/h at 25° C.;    -   Temperature 21° C.;    -   Relative humidity approximately 70%;    -   Cabin inlet airflow 77,872 Nm3/h        corresponding to 87,850 m3/h at 35° C.;    -   Temperature 25° C.;    -   Relative humidity 50±5%;

Considering an average of 60% efficiency for the heat exchanger, energyrecovery is approximately 206,350 kCal/h with a thermal differential ofapproximately 8.4° C. The inlet air is cooled by 8.4° C., so it wouldthen cool from 35° C. to 26.6° C.

The increase in energy recovery is significant and corresponds toapproximately 40% in these operating conditions.

Therefore, while the annual energy recovery with cross-flow only in theexample is approximately:

-   Hourly recovery=171.3 kW;-   Daily recovery=2,740.8 kW.

If the system and the humidification section according to the inventionare used, the recovery in electric kW (kW) of approximately 913.6 kWcorresponding to an energy recovery with cross-flow and humidificationas follows:

-   Hourly recovery=239.8 kW;-   Daily recovery 3,836.8 kW;-   Yearly electrical kW recovery of 1278.9 kW.

Therefore, it becomes evident from the example that the introduction ofa section of humidification in the treatment of exhausted air increasesconsiderably, at the same conditions, the volume of thermal recovery.

The system, as described, applies to thermally or thermohygrometricallycontrol painting cabins, surface preparation cabins, clean rooms andspecial cabins, and aims at improving energy recovery by humidifying theextraction air before treating it with a heat exchanger, e.g., across-flow or rotating type.

Obvious changes or variants may be made to the above description, insizes, shapes, materials, components and connections, as in the detailsof the illustrated execution and of the operating method withoutdeparting from the spirit of the invention, as noted in the followingclaims.

1. System to control a cabin, at least thermally including a first airtreatment unit (20) suitable to collect external air, treat external airand supply to the cabin (12) at least thermally controlled; a second airtreatment unit (30) suitable to extract from the cabin exhausted air ata set temperature; heat exchange means (43) configured to exchange heatbetween the exhausted air and external air as it is collected;characterized by whether second air treatment unit (30) includes airhumidification means (45) suitable to humidify exhausted air, to reduce,using evaporation enthalpy, the temperature of said exhausted air andsupply to exhausted air humidified in said heat exchange means. 2.System according to claim 1 characterized by whether said heat exchangemeans (43) are included in said second air treatment unit (30). 3.System according to claim 1 characterized by whether said second airtreatment unit (30) includes further extraction air treatment means (41)suitable to extract the exhausted air, filter it and supply it to saidair humidification means.
 4. System according to claim 1 characterizedby whether said first air treatment unit (20) includes at least acooling section (20 c) suitable to cool the air coming from said heatexchange means.
 5. System according the claim 4 characterized by whethersaid first air treatment unit (20) includes at least a section includedin the group of a ventilation section (20 a); an air heating section (20b); a humidification section (20 d); an air post-heating section (20 e);6. System according to claim 1 characterized by the fact that itincludes an external air filtering section (47) suitable to filter theexternal air to supply to the cabin (12) through the first air treatmentunit and/or an exhausted air filtering section (49) suitable to filterthe humidified exhausted air employed by said heat exchange means (43)and to discharge the humidified exhausted air outside the cabin. 7.Exhausted air treatment unit for a system to control at least thermallya cabin, including air treatment means (41) which may be connected tothe cabin and are suitable to extract exhausted air at a presettemperature; heat exchange means (43) configured to exchange heatbetween exhausted air and external air; characterized by airhumidification means (45) suitable to humidify said exhausted air, toreduce, using evaporation enthalpy, the temperature of said exhaustedair and supply to the humidified exhausted air into said heat exchangemeans (43).
 8. Exhausted air treatment unit, according to claim 7,characterized by whether said heat exchange means (43) are of thecross-flow or rotating type.
 9. Method to control at least thermally acabin, including the following phases: collect external air; treat atleast thermally said external air and supply, following treatment, airat least thermally controlled to the cabin; collect from the cabinexhausted air at a preset temperature; perform a heat exchange betweenthe exhausted air and the external air; characterized by the fact thatthe exhausted air collection phase includes the phase of humidificationof the exhausted air so as to reduce, using evaporation enthalpy, thepreset temperature of said exhausted air.
 10. Method according to claim9 characterized by the fact that the exhausted air collection phasefurther includes the phase of filtering said exhausted air.
 11. Methodaccording to claim 9 characterized by the fact that said phase oftreating at least thermally said external air includes the phase ofcooling the air before supplying it to said cabin.
 12. Method accordingto claim 9 characterized by the fact that it also includes at least oneof the phases of filtering the external air to supply to the cabin;and/or filtering the humidified exhausted air and discharging it outsidethe cabin.